Centaurs may not have reach, if they're classed as Large (Long) instead of Large (Tall). There's a chart in the Size, Space and Reach rules that lays out the difference. The Centaur in the Bestiary works that way. The Minotaur ought to get 10 feet of base reach with melee weapons, though.

Also, larger weapons don't inherently use larger damage dice in second edition. A Tiny greatsword does 1d12 damage, the same as a Huge greatsword. It's possible that Large creatures will get a permanent Clumsy 1 in exchange for a flat +2 damage the same way that Enlarge does, though. That's how they worked the feat-based size increase for Lizardmen. It's also possible they'll just get racial +2 Strength and -2 Dexterity or something instead.